Purification and pharmacological criteria will be developed for studying the isoenzymes of adenosine deaminase in normal and neoplastic tissues. Gel filtration with Sephacryl C-200, ion exchange chromatography with QAE-Sephadex and immunochromatography with anti-adenosine deaminase IgG-Sepharose will be employed. Pharmacological criteria for differentiating between the different molecular species of adenosine deaminase will be developed with inhibitors 2'-deoxycoformycin and erythro-9-(2-hydroxy-3-nonyl)adenine. The interconversion of the small molecular weight species to the large molecular weight enzyme via a conversion factor in liver will also be assessed.